Charge transport in nanoparticle chains influenced by stabilizer molecules

We have bridged a pair of gold electrodes through chains and arrays of gold nanoparticles (NPs), which were stabilized by a coating of citrate molecules. We performed a systematic and comparative analysis of current-voltage (I-V) characteristics for chains of NPs having variable lengths and configurations. Besides stochastic current fluctuations at a constant bias voltage and quasi-periodic fluctuations of the differential conductance arising from conformational changes of citrate molecules, we also observed that the arrangement and distribution of NPs can be changed by the applied electric field, contributing to conductance fluctuations and leading to irreversible changes and finally rupture of the conducting bridge. Although in all cases gold is bridged by the same citrate molecules, a significantly higher resistance between gold electrodes and the citrate coated gold NPs was found as compared to the resistance between identical NPs. This difference is attributed to the fact that citrate molecules are chemically attached to the NPs, but are only physically interacting with the electrodes. Thus, the resistance of the bridge is not only a function of the number of molecular contacts but also depends on the strength of the individual interactions between metal conductor and molecules.